Fetal Brain: Sex Differences in Gene Activity
- Molecular differences between male and female brains are largely established during the first trimester and persist throughout life,according to a new international study led by the University of...
- The research, published in Cell genomics, analyzed RNA sequence data from 1,899 human forebrain samples to create a timeline of sex-biased gene expression.
- The analysis revealed over 3,000 genes with differing activity between male and female fetal brains, compared to about 1,000 in adult forebrains.
scientists have discovered that the groundwork for sex differences in the brain,including differences in fetal brain wiring,is laid remarkably early,during the frist trimester of pregnancy. A groundbreaking study reveals over 3,000 genes exhibit varying activity between male and female fetal brains, these differences impacting life-long brain function. Researchers from the University of Helsinki’s FIMM found that prenatal hormonal influences considerably shape sex-biased brain biology. These insights are critical to understanding why neurological conditions affect men and women differently. The team analyzed RNA sequence data, creating a detailed timeline of sex-biased gene expression. For in-depth analyses of scientific discoveries, News Directory 3 has the scoop. Discover what future studies will reveal about the relationship between these early gene expression differences and susceptibility to neurological disorders.
Fetal Brain wiring Sets Up Life-Long Sex Differences, Study Shows
Updated May 27, 2025
Molecular differences between male and female brains are largely established during the first trimester and persist throughout life,according to a new international study led by the University of Helsinki’s Institute for molecular Medicine Finland (FIMM).
The research, published in Cell genomics, analyzed RNA sequence data from 1,899 human forebrain samples to create a timeline of sex-biased gene expression. The team used public RNA sequencing datasets, including prenatal specimens collected five to 17 weeks post-conception and adult samples from individuals aged 20 to 79.
The analysis revealed over 3,000 genes with differing activity between male and female fetal brains, compared to about 1,000 in adult forebrains. Statistical modeling indicated that nearly two-thirds of these differences are unique to early growth, while less than 1% emerge only in adulthood. The remaining differences persist across both life stages, though with smaller effects in adults.
researchers found that prenatal-specific sex differences were enriched for binding sites of androgen and estrogen receptors, highlighting the early hormonal influences in shaping sex-biased brain biology and fetal brain wiring.
“Our results show that the male–female gap in brain gene activity opens remarkably early, long before birth, and many of those early signatures stay with us,” said Clara Benoit-Pilven, a post-doctoral researcher at FIMM and the paper’s first author.
Benoit-Pilven added that understanding these fetal origins is crucial to understanding why neurological conditions frequently enough manifest differently in men and women. While the sex-biased genes themselves were not directly associated with neurological diseases, they appear over-represented in co-regulation networks linked to disorders like schizophrenia and multiple sclerosis. This suggests that subtle expression differences may modulate the activity of disease-associated gene networks,impacting fetal brain wiring.
The study also demonstrated that X-chromosomal genes escaping X-inactivation showed consistent female-biased expression throughout life, emphasizing the stable role of sex chromosomes in the brain.
“The findings underscore the importance of studying gene expression dynamics across development and aging to gain deeper insight into the molecular factors shaping phenotypic differences,” said Dr. Taru Tukiainen,former FIMM Group Leader and senior author of the study.
What’s next
Future research will focus on understanding how these early differences in gene expression and fetal brain wiring contribute to variations in brain structure, function, and susceptibility to neurological disorders across the lifespan.